The h Bar

Mostafa

00:06

@Slereah I don't think so. He had better reasons to do it if wanted to ;)

@0celo7 nothing.

I'd miss the joy

Dawood ibn Kareem

Ma shaa Allah, brother.

Mostafa

@DawoodibnKareem thanks :)

DanielSank

00:37

Hi, @Mostafa.

How's it going?

Mostafa

@DanielSank Hi

@DanielSank Fine, thanks

DanielSank

@Mostafa Ooof.

rough

Mostafa

@DanielSank oh it was a typo. It's 16.5 hours

The same user both asked this and answered this. strange.

DanielSank

Not so strange, I think.

The delta function stuff involves calculus and a somewhat subtle understanding of linear algebra.

The spin stuff is a lot simpler.

IMHO

Dawood ibn Kareem

00:54

The answer looks like he/she may have copied it from somewhere, at least partially. the question indicates that he/she is actually starting to think about things.

DanielSank

Hello, @DawoodibnKareem, we haven't met.

Dawood ibn Kareem

Hello Daniel. Right you are.

DanielSank

Are you a student?

Oh, I guess not.

Dawood ibn Kareem

No, it's been many years since I was a student.

I guess you've just looked at my profile, right?

DanielSank

yes

Mostafa

01:00

@DanielSank I am a BS in electrical engineering and knew that. How can someone with a Master's in theoretical physics not know this?

DanielSank

@Mostafa No idea.

People do and don't know all kinds of weird stuff.

I have a PhD in physics and you'd be surprised what I don't know :)

Mostafa

@DanielSank Yeah right. same for me (about basic electrical engineering stuff)

Dawood ibn Kareem

Remember that the goal of all the Stack Exchange sites is to build up a resource of useful questions and answers. There's no rule against asking a question that you already know the answer to, if it contributes to that goal.

DanielSank

@DawoodibnKareem you know what's funny about that? I got four downvotes for this:

4

Q: Consistent, complete, and generalized description of the quantum harmonic oscillator

Textbooks often introduce the quantum harmonic oscillator with the example of a mass on a spring, giving the Hamiltonian $$H = \frac{1}{2} k x^2 + \frac{1}{2m}p^2 \qquad [x,p] = i \hbar \, .$$ The raising/lowering operators are then introduced as $$a = \sqrt{\frac{m \omega_0}{2 \hbar}} \left( x +...

Dawood ibn Kareem

And 8 upvotes, apparently. It seems like a good question. Make that 9 upvotes :-)

Oh, I just realised you answered it too.

I should do that kind of thing occasionally on SO.

I don't know what it means to "accept" an answer on Physics.SE. I understand upvoting and downvoting. But surely, in most cases, the original querent is someone who doesn't know the correct answer. It makes no sense to me, to give that person a vote that's worth an additional 15 unicorn points.

It's not like Stack Overflow, where most of the questions are "how do I do XYZ" and the accepted answer is supposed to be the answer that the original querent actually used, and solved their problem for them.

Mostafa

01:11

@DawoodibnKareem Actually the secret to getting * a lot* of gold badges (famous question badge) is this: Ask as many very rudimentary question as you can.

even if they're close-worthy ;)

This is the list of the questions with over 200k views here: physics.stackexchange.com/search?q=views%3A200000

Dawood ibn Kareem

Right. People upvote questions that they understand.

However, I'm not really interested in getting a lot of gold badges. I only ask
questions if it's something my teenage son wants to know. And I only answer questions if I feel I can add something that hasn't already been covered by other answers.

Zophikel

01:41

Does anyone know good software for Quantum Infomration Simulation

Sir Cumference

@Cryolune Well the phases look like this:

Cryolune

I see.

well who cares about realism.

bolbteppa

$M \in SL(2,\mathbb{C}), \sigma_{\mu} M \overline{\sigma}^{\mu} = 2 \mathrm{tr}(M) I_{2,2}$?

Cryolune

yes

Dawood ibn Kareem

@SirCumference What's supposed to be unrealistic?

Sir Cumference

01:49

@DawoodibnKareem I dunno, fiction

Dawood ibn Kareem

Oh.

David Z

04:32

@DawoodibnKareem well, that's one of the goals. A major one, to be sure, but it's not the sole purpose of the site. (If it were, we'd probably just be a wiki)

@dmckee oh, I wasn't looking for support. The joke is that telnet is so irrelevant these days that I don't even have it installed.

Qmechanic

04:45

0

Q: A discussion about Quantum Gravity and Semiclassical Gravity

Ok. I really would like to start asking a "polemic" question for the people who work in GR and Semiclassical Gravity: Why we just simply do not embrace Superstring Theory? I mean: All the other fields have a quantum nature, Math have been guiding humanity since the beggining, why just we simply d...

quantum-mechanics general-relativity string-theory quantum-gravity

Unclear? Too broad? Primarily opinion-based?

David Z

@Qmechanic all of the above, probably. I'd choose POB as the primary reason for closure.

Sir

06:23

Hi

If i have the formula in computer code:
distanceTravelled = v0 * TotalFlightTime - dragCoefficient * TotalFlightTime * 2

Now, I am trying to find the total flight time elapsed for a given distance but not sure how to do so. does any one do much programming for this kind of stuff?

David Z

You don't need programming to do that, it's just basic algebra.

Avantgarde

07:38

@Sir You just write the formula in code. The program would hardly be more than a few lines long

user228700

08:20

@JohnR: Morning :-)

John Rennie

Hi :-)

user228700

How goes it?

user228700

@JohnR:

user228700

21 hours ago, by Kaumudi. H

Say, from where do u usually download subtitles?

user228700

?

John Rennie

08:27

Apologies for the high latency. I was writing some stuff on the SciFi stack exchange.

Let me check what subtitle site I've been using. Hang on a mo ...

user228700

OK :-)

John Rennie

Found it!

I use opensubtitles.org

user228700

Ah, OK. Thank you!! :-)

John Rennie

But be a little careful with this site as there is some spyware on it.

user228700

Dang. OK...

John Rennie

08:34

Suppose you were searching for subtitle to Deadpool (this is purely hypothetical of course :-). You search for "Deadpool" and get a page like:

To download the subtitles click on the link where I've indicated, or in that column on any of the subtitles, then wait and the download should start automatically.

When you click you'll be taken to another page, but don't click anything on that page. Just wait, and the subtitles should download without you needing to do anything further.

user228700

Damn, it's actually Greek or something.

John Rennie

The subtitles will probably download as a .zip file. Click the .zip file to open it and you should see a .srt file inside it, which is what you want.

@Kaumudi.H Oops yes, the third one down is English

The flags show the language

user228700

...and I am an idiot.

John Rennie

Well, I missed it as well :-)

user228700

Doesn't work :-/

John Rennie

08:42

@Kaumudi.H as in doesn't download, or the SRT file doesn't work?

user228700

The file. Timing isn't correct.

John Rennie

You'll find films often come in subtly different edits, and each edit needs its own subtitle file. You could try one of the other subtitle files in the listing to see if it's better. At the end of the day these are subtitles put together by enthusiasts so they come with no guarantee.

user228700

Yes, yes, I know...

user228700

Anyhoo. Thanks! :-)

Kenshin

is it legal?

user228700

08:47

Probably?

Jack Clerk

Good night everyone (it's almost dawn here in Brazil acctually).

Here it comes my question of the main site: https://physics.stackexchange.com/questions/341100/a-discussion-about-quantum-gravity-and-semiclassical-gravity

And here is the same question for the chat:

"Ok. I really would like to start asking a "polemic" question for the people who work in GR and Semiclassical Gravity: Why we just simply do not embrace Superstring Theory? I mean: All the other fields have a quantum nature, Math have been guiding humanity since the beggining, why just we simply do not embrace the concept of a …

from the main site**

Kenshin

polemic questions are frowned upon

Sid

Anyone here interested in Cryptic Crosswords?

Kenshin

No

We're interested in the physical world, not the words

words are meaningless if not to describe the physical world

Jack Clerk

Mr Kenshin, did you read the question? Have you some opinion?

Kenshin

08:49

@JackClerk yes I did read the question

Superstring theory is wrong, that's why we don't embrace it

@JackClerk you must understand, gravity isn't a "field" it is the nature of the spacetime fabric itself

Jack Clerk

I see. You work with gravity?

John Rennie

Hi @JackClerk

Jack Clerk

Hello @JohnRennie

John Rennie

There are some major conceptual issues with quantum gravity that we have very little idea how to solve.

Right now it's too early to say with confidence that any of the theories of quantum gravity are likely to be the ultimate theory.

Kenshin

Yes I work with gravity

John Rennie

08:56

Reading the popular science press will give you the idea there are quantum gravity wars with opposing sides fighting for their own theory, but the reality isn't like that. Right now there is no theory that successfully describes the classical limit i.e. general relativity.

Kenshin

Everyone works with gravity when they stand up

John Rennie

I can't speak for all physicists but I suspect most would agree with me that it's far too early to pick sides, and most of us have an open mind.

Jack Clerk

Yes, I agree with you. But, I would like to explore more about Semiclassical Gravity, because It seems more "stable" to do some science.
Also, some people already told me that Semiclassical Gravity (or QFT in curved spacetimes following the sense of Wald and Parker books, and the "habitat" of black hole themodynamics and so on) IS NOT an Quantum Gravity research.

Kenshin

@JohnRennie do you think people are progressing on the problem? or just waiting to have an aha moment?

Jack Clerk

and inthe "habitat"**

But still deals with quantum effects like Unruh Effect. It's a little bit confunsing to me.

John Rennie

08:59

@JackClerk semiclassical gravity uses the expectation value of the quantum stress-energy tensor in the field equations, but this can only ever be an approximation. For example it isn't clear how we write the equations for a source that is in a superposition.

Jack Clerk

Cool, that's quite interesting.

John Rennie

With the Hawking/Unruh effect it isn't really semiclassical gravity because it ignores backreaction. This is generally described as quantum field theory in a curved background.

Quantum field theory in curved spacetime

In particle physics, quantum field theory in curved spacetime is an extension of standard, Minkowski space quantum field theory to curved spacetime. A general prediction of this theory is that particles can be created by time-dependent gravitational fields (multigraviton pair production), or by time-independent gravitational fields that contain horizons. == Description == Interesting new phenomena occur; owing to the equivalence principle the quantization procedure locally resembles that of normal coordinates where the affine connection at the origin is set to zero and a nonzero Riemann tensor...

Kenshin

@JackClerk why do you want to work with quantum gravity?

Jack Clerk

This is strange, I've read some articles that said that Quantum Field Theory in a curved background is a synonym to Semicalssical Gravity

@Ken

John Rennie

Semiclassical gravity is the approximation to the theory of quantum gravity in which one treats matter fields as being quantum and the gravitational field as being classical.

Though the terms aren't precisely defined and different people may use them in different ways.

Jack Clerk

09:06

@JohnRennie that's is an phrase that I've heard many times!

Slereah

The trick is basically that semiclassical gravity is QFT in curved spacetime + the EFE

$$R_{\mu\nu} - \frac{1}{2}R g_{\mu\nu} = \langle \psi, \hat T_{\mu\nu} \psi \rangle$$

@JohnRennie the equation for a superposition is perfectly well defined

But!

It's one of the very few quantum gravity experiment we've actually done

The superposition of two quantum states for semiclassical gravity

And obviously it didn't work

Jack Clerk

But, just in a rougly point of view, assuming the spacetime something "classical" or "fundamental" is really right? I mean, why we should not expect another fundamental "thing" in quantum level that lead us to space-time as we know today?

Slereah

I think the results are slightly controversial but I think overall nobody believes that semiclassical gravity is true

@JackClerk Well yes, but how

That's the real issue

Jack Clerk

roughly**

Slereah

It's fairly hard to do

John Rennie

09:11

@JackClerk there have been suggestions that spacetime is an emergent phenomenon. But then there have been suggestions of all sorts, none of which have any realistic claim to be the one true theory.

Entropic gravity

Entropic gravity, also known as emergent gravity, is a theory in modern physics that describes gravity as an entropic force—a force with macro-scale homogeneity but which is subject to quantum-level disorder—and not a fundamental interaction. The theory, based on string theory, black hole physics, and quantum information theory, describes gravity as an emergent phenomenon that springs from the quantum entanglement of small bits of spacetime information. As such, entropic gravity is said to abide by the second law of thermodynamics under which the entropy of a physical system tends to increase over...

Slereah

Also recent measurements makes it unlikely that spacetime is discrete, too

Entropic gravity doesn't have spacetime as emergent

Only gravity

It still works in a fixed background

Jack Clerk

@Slereah could you please point me some of these mesuraments?

John Rennie

@Slereah it's currently formulated in a fixed background ...

Slereah

@JohnRennie Well yes

Entropic gravity in a curved background would be weird

Modern searches for Lorentz violation

Modern searches for Lorentz violation are scientific studies that look for deviations from Lorentz invariance or symmetry, a set of fundamental frameworks that underpin modern science and fundamental physics in particular. These studies try to determine whether violations or exceptions might exist for well-known physical laws such as special relativity and CPT symmetry, as predicted by some variations of quantum gravity, string theory, and some alternatives to general relativity. Lorentz violations concern the fundamental predictions of special relativity, such as the principle of relativity, the...

Jack Clerk

I've heard some hard counterpoint about verlinde's gravity. From Lubos and Sabine I guess.

Slereah

09:15

Lubos has hard counterpoint for anything that isn't string theory

John Rennie

@JackClerk you'll hear all sorts of stuff shouted over the Internet, but you're just hearing the tiny fraction of physicists who shout loudest. They aren't representative.

Kenshin

I heard the earth was flat

John Rennie

@Kenshin It is! (locally :-)

Kenshin

There you have it people, the earth is flat

John Rennie

Locally

Kenshin

09:17

yeah in fine print

Slereah

Lubos should really update his blog to include a latex plugin

Kenshin

@JohnRennie how did you find out about entropic gravity?

John Rennie

Can't remember. The idea has been floating around for years.

Kenshin

@JohnRennie so if entropic gravity is right, does that mean QFT and GR have now been unified?

Jack Clerk

I agree with you,again John.
Just to point out my situation: I'm in Undergraduate level, and I'm still need to start to study Relativity and QM so my questions are just "for fun" I mean: I want to know where to do the best shot to persue in my career (But this is just part of the reason to think about Semiclassical Gravity).

Kenshin

09:20

@JackClerk perhaps finance?

John Rennie

@Kenshin The current entropic gravity theories don't explain the origin of the microstructure responsible for the entropy, so they are purely phenomenological. They are far from anything like a unified theory.

Kenshin

I see ty

John Rennie

@JackClerk learn QFT first then see how much you like it. In fact start learning it now. QFT is entry level for this kind of work and unless you're comfortable with it you're going to struggle.

Jack Clerk

Before GR?

Slereah

Let me get my usual graphic

Kenshin

09:23

Learn GR first

John Rennie

Yes. GR is far easier then QFT.

If you have the horsepower to learn QFT you'll find GR easy.

Slereah

Kenshin

@JohnRennie to clarify you're saying learn GR first right?

Slereah

I'd say learn things concurently

Kenshin

no way

learn one thing at at time

Slereah

09:24

Advanced GR is much harder than basic QFT

Kenshin

no way

Jack Clerk

Acctually I like GR more than QFT.

John Rennie

@Kenshin No, I'm saying learn QFT first.

Jack Clerk

But

I don't know.

I need basic Math before.

Kenshin

@JohnRennie but you can learn GR quickly so why spend years learning QFT and not knowing GR, when you can quickly learn GR then spend years learning QFT but at least you have GR down pat

Slereah

09:25

that would be a good step, too

Learn to count

very important

staff.science.uu.nl/~hooft101/theorist.html

John Rennie

@JackClerk GR is vastly more elegant that QFT. By comparison with GR QFT is a pile of badly fitting pieces joined together with rusty nails :-)

Slereah

cf this

@JohnRennie obviously we're not reading the same GR :p

Kenshin

GR is a masterpiece

Dawood ibn Kareem

@Sir That formula doesn't look right to me. Drag coefficient should be dimensionless. Also, if that's ^2 rather than *2 at the end, you may need the quadratic formula.

John Rennie

@Slereah really? Classical GR is inelegant?

Kenshin

09:27

If you learn QFT before GR you will never learn GR

because it takes a lifetime to learn QFT

but it only takes a month to learn GR

Slereah

@JohnRennie It can be quite messy

Kenshin

@Slereah only in application

but we're not engineers so that's ok

Slereah

I'm currently reading a paper on non-differentiable metrics

It's not pretty

Avantgarde

No, it doesn't take a month to learn GR. Where'd you get that from?

Kenshin

@Slereah yeah I think the universe is differentiable

@Avantgarde from my professor why?

Slereah

09:29

Your professor probably doesn't know GR :p

Avantgarde

^

Kenshin

@Slereah How does he publish papers in it?

John Rennie

@Kenshin No it doesn't. QFT courses take only a semester - maybe a year. The point is that unless you can master QFT the whole project is a bust, so learn QFT first and if you find you hate it (or fail at it!) you've minimised the time wasted.

Slereah

@Kenshin itisamystery.com

Kenshin

@Slereah well whether he "understands" it or not, I guess he can paraphrase and say "it only takes a month to know enough GR to produce publishable works" in the field

John Rennie

09:31

>it only takes a month to know enough GR to produce publishable works

Avantgarde

It's very vague what 'publishable' means here

John Rennie

The term bollocks springs to mind :-)

Slereah

Well I mean if all he does is just numerical simulations

maybe

Kenshin

@Avantgarde well (1) You stated my professeur doesn't understand GR, (2) My professeur publishes in GR. So how do you reconcile these?

Avantgarde

I didn't state that. What I am saying is that you can't learn GR in a month. If that was even true, GR courses wouldn't run for a semester. They'd wind up within a month

Kenshin

09:33

You can't teach GR to a class in a month

but a student can learn it in a month

Classes have to be slower because the teacher can't demand too much of the students

Avantgarde

Ok

I think we scared him away

John Rennie

I think you could certainly get a good understanding of GR in a month. But this would be far from mastery of the subject.

Kenshin

Have you never felt you could learn things faster than the normal progression of the course?

Jack Clerk

Anyway, thanks everyone for the anwsers.
I think that the path: GR---->QM---->QFT seems more "linear"

Kenshin

@JohnRennie yeah we're not talking about mastery, it can take a lifetime to master many subjects

@JackClerk I would say QM then GR then QFT

Slereah

09:35

QM is (mostly) easy

If you do it the physicist way, that is

and don't worry about projection valued measures

John Rennie

@Kenshin OK, to learn it well enough to be able to publish original research would take far longer than a month.

Kenshin

@JohnRennie how long would that take?

Balarka Sen

This particular topic aside, it seems to me you're slowly going from philosophically analytical to increasingly opinionated while discussing things in this chat. I usually ignore users who do the latter.

Just sayin'

Kenshin

@BalarkaSen yeah I'm not a one trick pony

Avantgarde

ba dum tshh

Kenshin

09:39

but that said I do have analytical reasons to back up my opinions, but I'll leave that as an exercise to the reader

Avantgarde

What will happen if I click "enable desktop notification"?

I don't want to click it and then enable a lifetime of pinging, being unable to find how to revert it

Balarka Sen

vov

Kenshin

I"m sure you'll figure out how to revert it

Avantgarde

I have a tough time believing matters related to buttons located at remote corners of the screen

John Rennie

@Avantgarde click it and the link changes to disable desktop notifications

Dawood ibn Kareem

09:41

You can revert it in your browser settings if you need to.

Avantgarde

@JohnRennie Great, thanks for the answer

John Rennie

@Avantgarde all the link does is change your browser settings for notification. You can always revert it in the browser settings. In Chrome that's Settings/Advanced/Content. In other browsers I'm sure the solution is just a Google away.

Kenshin

@JohnRennie why don't advance physics textbooks contain pictures like the undegraduate books do?

Avantgarde

@JohnRennie Okay, thanks for the info!

Slereah

they do

Not all of them but they do

Kenshin

09:45

All the one's I've read are just walls of text

maybe an occosaional black and white simplicistic figure

Slereah

depends on the topic

Kenshin

but not photographs and coloured headings etc.

Slereah

Photographs of what

You can't photograph a category

Balarka Sen

@Slereah fun idea tho

Avantgarde

Like a pic of the LHC in a particle physics book?

Kenshin

09:46

exactly

just some nice pictures to make the book more enjoyable to look at

Slereah

Maybe because it's not a children book

Balarka Sen

ma.utexas.edu/users/a.debray/lecture_notes/m392c_EHT_notes.pdf

Slereah

great cover

I did want to give my CTC book this cover*

Balarka Sen

i would read that book

Kenshin

Do you like children's books Balarka?

Balarka Sen

09:56

depending on the book, sure

and depending on the children

John Rennie

A book of recipes for children would be nice :-)

Balarka Sen

I have a compilation of Russian fairy tales I still recommend pretty much literally anybody. Kayum Tangrykuliev's stories are p good too.

Slereah

Do you mean like

DAS KAPITAL

Balarka Sen

Fantastic book

I also like ze communist manifesto

quick and dirty

Dawood ibn Kareem

Does the communist manifesto have photographs and brightly coloured headings?

Balarka Sen

10:04

you can make custom made drawings

the headlines are colored with red

Kenshin

is communism a religion?

Balarka Sen

depending on the definition of religion

Dawood ibn Kareem

Christian communism

Christian communism is a form of religious communism based on Christianity. It is a theological and political theory based upon the view that the teachings of Jesus Christ compel Christians to support communism as the ideal social system. Although there is no universal agreement on the exact date when Christian communism was founded, many Christian communists assert that evidence from the Bible suggests that the first Christians, including the Apostles, established their own small communist society in the years following Jesus' death and resurrection. As such, many advocates of Christian communism...

Secret

Last night dream:

Kenshin

a cell?

Secret

10:10

NB The diamonds are already less than 1 pixel wide in this pics, thus I have no idea how to actually drew them all without the whole think looking like a rocky texture

That thing is some kind of pendant, made of purple crystals and with small diamonds all over the rest of it

Kenshin

what's the context of the dream?

Secret

The pendant is called Crystal of Tears. It is a very powerful artifact that is formed by some kind of pure positive emotion. In the dream, a boy tries to save his mother from being killed by fate, and the love manifest itself and crystalised into this artifact

Kenshin

cool

John Jack

11:58

@Mithrandir24601 Hey how's it going?

Secret

13:25

0

Q: The eigenvalue equation and its physical interpretation in the frames of quantum mechanics

I have taken my first course on quantum mechanics, in order to get ready for the Monday test, I am trying to solve the previous year test. One of the points is as in the title, I am going to present my answer and I want to know, whether it is correct and complete. Moreover I would like to read ...

quantum-mechanics schroedinger-equation eigenvalue

Example of an "am I right" question where the title will mislead you to think it is something deep

Dawood ibn Kareem

He hasn't actually stated what the question was. He's just presented his answer and asked whether it's sufficient. How can anyone possibly know, unless they've also seen the exam question?

0celo7

13:40

@JohnRennie I would like to put this to the test

give me some motivated physics students and a month

and a large whiteboard

@Kenshin what is a professeur?

@JohnRennie it's both

if you want to work with the actual Einstein equations it's a mess

if you do other stuff it's better

@Kenshin what does "only in application" mean

Danu

15:17

@0celo7 nope.jpg :P

So, regarding the tikz question, do you know how to shift arrows right/left? Did you try that?

0celo7

@Danu oops, got distracted and forgot about that

I don't know, no

Danu

shift left or shift left=1,2,3,4,... whatever you prefer

0celo7

nice, but it's not completely centered on the $N$ now

should I shift the other one right?

can I do half steps?

wonderful, thanks!

Balarka Sen

@Blue Why is p-chloro toluene produced in greater percentages than the ortho-isomer while halogenating benzene?

Danu

@0celo7 You can do shift lef=1.125pt for all tikz cares :P

0celo7

15:32

@Danu good to know

Balarka Sen

@Blue I would think CH3's +I effect would be increasing the electron density at the ortho position, thereby making it a stronger attacking position for Cl.

Danu

@0celo7 Custom length specification as well as "step-by-step" input works in essentially all tikz functions

0celo7

@Danu My goal is to never wander far enough from analysis to have to do anything more complicated than the diagram above :)

Danu

@0celo7 What a terrible thing to say.

Also, you're screwed if you wanna learn the Atiyah-Singer index theorem :p

Balarka Sen

you could just write that diagram on paper and scan it

done and done

0celo7

15:39

@Danu Gilkey has zero commutative diagrams.

Danu

@BalarkaSen Not if you want to present the document to... anyone important :P

@0celo7 They're still there, implicitly.

0celo7

I wasn't saying they're not important

I'm saying I don't want to typeset them

Important distinction

Balarka Sen

handwritten diagrams are beautiful. those important people will love them

Danu

@0celo7 fair enough

@BalarkaSen Your trolling is getting pretty old; I'm not going to respond anymore :P

0celo7

@BalarkaSen I went to a sphere packing lecture that was hand written on an iPad pro

Balarka Sen

15:42

You just did, @Danu

win win

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